Parts distributing method

ABSTRACT

A parts distributing method for distributing parts to mounting units in a parts mounting system having a plurality of mounting units. The method involves specifying parts of specific kinds which can be mounted with each mounting unit as division-specified parts; distributing parts specified for a specific mounting unit to the specific mounting unit; repeating operations to distribute parts having a maximum mounting time, out of remaining parts other than the division-specified parts, to mounting units which sequentially have a minimum mounting time; and repeating operations to distribute the division-specified parts one by one to mounting units which sequentially have a minimum mounting time.

FIELD OF THE INVENTION

The present invention relates to a parts distributing method fordistributing electronic parts to mounting units in a mounting systemwhich comprises a plurality of parts mounting units connected theretofor mounting the electronic parts on a printed circuit board and amounting system which carries out the parts distributing method.

BACKGROUND OF THE INVENTION

In the recent years where diversified kinds of electronic parts are fedin diversified modes and a larger number of electronic parts are mountedon each printed circuit board in the field of electronic parts mounting,it is often practiced to manufacture a printed circuit board with aparts mounting system which comprises a plurality of mounting units forelectronic parts of plural kinds or a single kind.

Employed as a method to prepare operating instruction data for mountingunits for electronic parts (“operating instruction data for the mountingunits for the electronic parts” will hereinafter be referred to simplyas mounting data) is a method for preparing mounting data by inputtingsuch data as on location, dimension and the like of the electronic partsto a CAD system intended for designing a printed circuit board formounting electronic parts, in an attempt to prepare mounting dataefficiently and with higher precision.

In order to operate a plurality of mounting units for electronic parts(“the mounting units for electronic parts” will hereinafter be referredto simply as mounting units) with high efficiency by equalizing mountingtime with each mounting unit as much as possible, however, it isnecessary to employ a method for determining which parts are to bedistributed to which mounting units.

Description will be made of a method for distributing electronic partsto the mounting units in a known electronic parts mounting system.

1. In mounting data for a single printed circuit board, an electronicpart of a kind specified for a specific mounting unit (“the electronicpart which is specified for a specific mounting unit” will hereinafterbe referred to simply as a fixed part) is distributed to the specifiedmounting unit and such a distribution is repeated until no fixed partremains.

2. Then, a mounting time of each mounting unit to which the fixed partshave been distributed is calculated, and a mounting time for eachremaining kind of electronic parts is calculated by multiplying a numberof the parts by a mounting time for each single part.

3. Then, an electronic part which is calculated to have a the maximummounting time is distributed to a mounting unit having the minimummounting time, and such a distribution is repeated until no electronicpart remains.

Thus, all the electronic parts are distributed to the mounting unitssuch that each unit will have an equalized mounting time.

However, the foregoing known parts distributing method poses problemswhich are described below.

This method allows electronic parts of one kind to be distributed onlyto a single mounting unit. Therefore, when the kinds of electronic partsto be mounted on a single printed circuit board is in a small number andthere are a large number of electronic parts of a same kind, it is hardto sufficiently equalize the mounting time of each mounting unit.

DISCLOSURE OF THE INVENTION

It is therefore a primary object of the present invention to solve theabove-described problems and to provide a parts distributing methodwhich is capable of equalizing a mounting time with each mounting unitand a mounting system for carrying out said method.

For accomplishing this object, the present invention provides a partsdistributing method for distributing parts to mounting units in amounting system having a plurality of mounting units, said methodcomprising the steps of:

specifying parts which can be mounted with each of the mounting units asdivision-specified parts; distributing parts specified for a specificmounting unit to the mounting unit; repeating operations to distributeparts having a maximum mounting time, out of remaining parts other thanthe division-specified parts, to the mounting units which sequentiallyhave a minimum mounting time; and repeating operations to distribute thedivision-specified parts one by one to the mounting units whichsequentially have a minimum mounting time.

According to the configuration described above, the parts distributingmethod of the present invention is capable of reducing variations inparts mounting time among the mounting units by specifying the specificparts as the division-specified parts and finally distributing saiddivision-specified parts one by one to the parts mounting units.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an electronic parts mountingsystem in an embodiment of the present invention;

FIG. 2 is a plan view illustrating a printed circuit board on whichelectronic parts are to be mounted in the embodiment of the presentinvention; and

FIG. 3 is a flow chart illustrating an electronic parts distributingmethod employed in the embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

Now, embodiments of the parts distributing method and the mountingsystem according to the present invention will be described withreference to FIGS. 1 through 3.

The electronic parts mounting system has an electronic parts mountingunit 1 for mounting specific small electronic parts at high speeds (“theelectronic parts mounting unit for mounting specific small electronicparts at a high speed” will hereinafter be referred to simply as ahigh-speed mounting unit) and an electronic parts mounting unit 2capable of mounting various electronic parts having special forms (“theelectronic parts mounting unit capable of mounting various electronicparts having special forms” will hereinafter be referred to simply as amulti-function mounting unit), which are connected to the system asshown in FIG. 1, and further comprises a parts distributor unit 4 whichgenerates “distribution data” for distributing a plurality of electronicparts to be mounted on a single printed circuit board 3 as shown in FIG.2 between the high-speed mounting unit 1 and the multi-function mountingunit 2, and a keyboard 5 which inputs data of the electronic parts to bemounted on the printed circuit board 3 into the parts distributor unit4. The plurality of electronic parts to be mounted on the printedcircuit board 3 are shared between the high-speed mounting unit 1 andthe multi-function mounting unit 2.

The parts distributor unit 4 is comprised of a micro compute whichcomprises: an input section 11 into which data is input from a keyboard5; a parts memory 12 which stores data of a plurality of electronicparts to be mounted on a single printed circuit board 3, that is, anumber of electronic parts, kinds thereof and tacts (mounting time perelectronic part) for each of the mounting units 1 and 2; a memory 13 fora high-speed mounting unit and a memory 14 for a multi-function mountingunit which respectively store the “distribution data” to be distributedto the mounting units 1 and 2; an output section 15 which outputs thedistribution data stored in the memories 13 and 14 to the high-speedmounting unit 1 and the multi-function mounting unit 2 respectively; anda distributor section 16 which will be described later in detail.

Description will be made of mounting operations in which six electronicparts A, five electronic parts B, five electronic parts C and fourelectronic parts D are mounted on the printed circuit board 3 as shownin FIG. 2.

The tacts employed for mounting the electronic parts A, B, C and D withthe respective mounting unit 1 and 2 are summarized in Table 1. In Table1: the electronic part A requires 0.15 second to be mounted with thehigh-speed mounting unit 1 arid 0.25 second to be mounted with themulti-function mounting unit 2; the electronic part B requires 0.20second to be mounted with the high-speed mounting unit 1 and 0.30 secondto be mounted with the multi-function mounting unit 2; the electronicpart C which has a special form and therefore can be mounted only withthe multi-function mounting unit 2 requires 0.40 second to be mounted;and the electronic part D requires 0.15 second to be mounted with thehigh-speed mounting unit 1 and 0.25 second to be mounted with themulti-function mounting unit 2.

The data on parts to be mounted on the printed circuit board 3 describedabove is input into the distributor section 16 by manipulating thekeyboard 5 and stored into the parts memory 12 by the distributorsection 16. The electronic parts A which are used in a large number andcan be mounted with either of the mounting units 1 and 2 arepreliminarily set as “divisible” in the parts memory 12 as division databy manipulating the keyboard 5.

Procedure for distributing the electronic parts A, B, C and D in thedistributing section 16 to the mounting units 1 and 2 in the conditionsdescribed above will be explained with reference to the flow chart shownin FIG. 3.

First, the distributor section 16 distributes fixed parts to themounting units 1 and 2 based on the parts data for the printed circuitboard 3 stored in the parts memory 12. In this embodiment, the fiveelectronic parts C which can be mounted only with the multi-functionmounting unit 2 are distributed to the multi-function mounting unit 2and stored in the memory 14 for the multi-function mounting unit (step#1). Though only one kind of fixed parts are specified for the mountingunits 1 and 2 in this embodiment, this step is repeated until no fixedpart remains when plural kinds of fixed parts are specified for themounting units (step #2).

Then, the time for mounting the electronic parts distributed in steps #1and #2 are calculated (step #3). In this embodiment wherein fiveelectronic parts C are to be mounted with the multi-function mountingunit 2, the mounting time of the multi-function mounting unit 2 is setat 0.4×5=2.0 seconds.

Then, electronic parts which have a maximum value of time obtained bymultiplying the number of the parts by a mounting time per electronicpart (the electronic parts B in this embodiment, since the electronicparts B require a mounting time of 5×0.2=1 and the electronic parts Drequire a mounting time of time of 4×0.15=0.6), out of the remainingelectronic parts other than the division-specified parts which arepreliminarily set as “divisible” as division data (electronic partsother than the electronic parts A, that is, the electronic parts B andD), are distributed to a mounting unit having the shortest mounting timeas a result of adding every mounting time for each mounting part whichhas been distributed at the step #1 to the mounting time calculated atthe step #3 (the mounting unit 1 which has a mounting time of 0) andstored in a memory (the memory 13 for the mounting unit 1. which has themounting time of 0) (step #4). At step #5, the part distributor unit 4judges whether or not there is a remaining electronic part other thanthe division-specified parts. In this embodiment wherein the electronicparts D remain, the parts distributor unit 4 returns to the step #3 andcalculates a mounting time of each of the mounting units by totalizingthe mounting time for the distributed electronic parts. Speakingconcretely, the mounting unit 1 which mounts the electronic parts B hasa mounting time of 5×0.2=1 second, whereas the mounting unit 2 whichmounts the electronic parts C has a mounting time of 5×0.4=2 seconds. Atthe next step #4, the parts distributor unit 4 distributes the remainingelectronic parts (the electronic parts D) to the mounting unit which hasthe shortest mounting time (the mounting unit 1) and stores them in thememory (the memory 13 for the mounting unit 1 which has the mountingtime of 0). The procedure described above is repeated until thereremains no electronic part other than the division-specified parts.

When there remains no electronic part other than the division-specifiedparts, the part distributor unit 4 calculates the mounting time of eachmounting units 1 and 2 after the electronic parts described above havebeen distributed (step #6). In this embodiment, the mounting unit 1which mounts the electronic parts B and D has a mounting time of5×0.2+4×0.15=1.6 seconds and the mounting unit 2 which mounts theelectronic parts C has a mounting time of 2 seconds as described above.On the basis of difference in mounting time, the division-specifiedparts (electronic parts A) are distributed one by one to the mountingunit having a shorter mounting time (first to the mounting unit 1 whichhas the mounting time of 1.6 seconds) and stored in the memory (first inthe memory 13 for the mounting unit 1 which has the mounting time of 1.6seconds) (step #7). Until the parts distributor unit 4 judges that nodivision-specified electronic part remains at step #8, it repeats theoperations to return to the step #6 for calculating the mounting time ofthe mounting unit by adding up a mounting time per distributedelectronic part and distributes an electronic part to the mounting unitwhich has a shortest mounting time at the step #7, thereby distributingall remaining division-specified electronic parts. Thus, all theelectronic parts are distributed to the mounting units. When the firstthrough third electronic parts A have been distributed sequentially tothe mounting unit 1 in this embodiment, the mounting unit 1 has amounting time of 1.6+0.15×3=2.05 seconds which is longer than that ofthe mounting time of 2.0 seconds of the mounting unit 2. Then, the nextfourth electronic part A is distributed to the mounting unit 2, and thenthe mounting unit 2 has a mounting time of 2.0+0.25=2.25 seconds. Then,the fifth electronic part A is distributed to the mounting unit 1, andthen the mounting unit 1 has a mounting time of 2.20 seconds, so thatthe last sixth electronic part A is distributed to the mounting unit 1.

As a result, the mounting unit 1 is set to mount five electronic partsA, the electronic parts B and the electronic parts D. Whereas, themounting unit 2 is set to mount one electronic part A and the electronicparts C. In this case, the mounting unit 1 has a mounting time of 2.35seconds and the mounting unit 2 has a mounting time of of 2.25 seconds.

In the conventional example wherein the electronic parts A, B and D aremounted with the mounting unit 1 and the electronic parts C are mountedwith the mounting unit 2, the mounting unit 1 has a mounting time of 2.5seconds and the mounting unit 2 has a mounting time of 2.0 seconds,thereby producing a large variation between the mounting times andrendering the mounting efficiency to be lower than that in theembodiment of the present invention.

When all the electronic parts A, B, C and D are distributed to thememories 13 and 14, respectively for the mounting unit 1 and themounting unit 2, distribution data stored in these memories 13 and 14are output to the output section 15, which outputs the distribution datato each of the mounting units 1 and 2 (at step #9) to complete theprocedure.

Exemplified in the above-described embodiment, for simplicity ofdescription, is a mounting system which includes two mounting units,that is, the high-speed mounting unit 1 and the multi-function mountingunit 2. It is needless to say, however, that the present invention isapplicable to a mounting system which includes three or more mountingunits.

As clear from the foregoing description, it is possible to reduce avariation between mounting times of the mounting units 1 and 2 forefficient operations of these mounting units by way of preliminarilyspecifying specific electronic parts as division-specified parts, firstdistributing a fixed part specified for a specific mounting unit to saidmounting unit, sequentially repeating operations to distribute a parthaving a maximum mounting time, out of remaining parts other than thedivision-specified part, to the mounting unit which sequentially has aminimum mounting time, and finally distributing the division-specifiedparts one by one to each of the mounting units.

TABLE 1 Tacts for high-speed Tacts for multi-function Part name Quantitymounting unit mounting unit Electronic 6 0.15 0.25 PartA Electronic 50.20 0.30 PartB Electronic 5 — 0.40 PartC Electronic 4 0.15 0.25 PartDTact:mounting time per part(sec.)

What is claimed is:
 1. A parts distribution method for distributingparts to mounting units in a mounting system having a plurality ofsimultaneously movable mounting units, said method comprising:specifying a) a first category of parts comprising a largest number ofparts to be mounted with any of said mounting units; b) a secondcategory of parts that require mounting with a specific mounting unit;and c) a third category of parts that are mountable by at least onemounting unit but not by all of the mounting units, said third categoryof parts comprising parts other than the parts from said first andsecond categories; distributing said second category of parts to saidspecific mounting unit and calculating a cumulative mounting time forsaid specific mounting unit to which said second category of parts fromany of said first, second and third categories of parts has beendistributed; determining a distribution time for said third category ofparts based on a respective mounting time to thereby distribute saidthird category parts so that each part of said third category of partshaving a longer mounting time than remaining parts of said thirdcategory of parts is distributed sequentially to mounting units having ashortest cumulative mounting time among said mounting units for mountingall of said third category of parts and updating a cumulative mountingtime for each mounting unit receiving a part from said third category ofparts; and determining a distribution time for said first category ofparts to thereby distribute said first category of parts one by one to amounting unit having a shortest cumulative mounting time as determinedafter each respective distribution of a part from said first category ofparts.
 2. A parts distribution method for distributing parts to mountingunits in a mounting system having a plurality of simultaneously movablemounting units, said method comprising: specifying a) a first categorycomprising a largest number of parts to be mounted with any of saidmounting units; b) a second category of parts that require mounting witha specific mounting unit; and c) a third category of parts that aremountable by at least one mounting unit but not by all of the mountingunits, said third category of parts comprising parts other than theparts from said first and second categories of parts; distributing saidsecond category of parts to a specific mounting unit and calculating acumulative mounting time for said specific mounting unit; determining adistribution time for the third category of parts based on a respectivemounting time to thereby distribute said third category of parts so thateach part of said third category having a longer mounting time thanremaining parts of said third category of parts is distributedsequentially to mounting units having a shortest cumulative mountingtime said among mounting units for mounting all of said third categoryof parts and updating a cumulative mounting time for each mounting unita part from said third category of parts; and determining a distributiontime for said first category of parts to thereby distribute said firstcategory of parts one by one to a mounting unit having a shortestcumulative mounting time as determined after each respectivedistribution of a part from said first category of parts.